Human Neurobiology 217 Prof Stuart Bunt [email protected] Professor Stuart Bunt 217.
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Transcript of Human Neurobiology 217 Prof Stuart Bunt [email protected] Professor Stuart Bunt 217.
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Human Neurobiology 217
Prof Stuart [email protected]
Traditional Anatomy• Phrenology, the study of
bumps on the skull.
• Measuring brain weights and size (still being done..see the fuss about Einstein’s brain).
• Little link between morphology and performance
• Neanderthal > Homo sapiens
• Hydrocephalic genius
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Human Neurobiology 217
Prof Stuart [email protected]
Plane Film X-rays
• Not very good for showing soft tissues
• Can show bone erosion• Large space filling masses
may be picked up if they have largely differing X-ray absorption
• Bone of skull requires high energy for penetration
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Human Neurobiology 217
Prof Stuart [email protected]
Contrast Media
Myelogram
CAT with media around cord
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Human Neurobiology 217
Prof Stuart [email protected]
Ventriculogram
• Air is introduced into the ventricles via the lumbar cistern (in adults)
• Via the fontanelles in infants• Patient placed on a tilting
table, air fills ventricles• Can detect “space filling”
lesions.• Causes severe headaches,
same dangers as lumbar puncture.
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Human Neurobiology 217
Prof Stuart [email protected]
Subtraction Angiography• Radio opaque medium is
introduced into the internal carotid artery or systemically.
• Iodine compounds can promote allergic reactions, any arterial invasion dangerous.
• Subtract X-ray before contrast medium from X-ray with contrast medium.
• Can pick up any abnormality of the blood vessels.
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Human Neurobiology 217
Prof Stuart [email protected]
Direct Stimulation
• During operations surgeons may have to delimit crucial areas.
• Epilepsy often spreads from a temporal lobe focus
• The speech area on the planum temporale must be identified.
• Cortex stimulated in conscious patient
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Human Neurobiology 217
Prof Stuart [email protected]
Computerised Axial Tomography• Many X-rays are taken
around the head (or body)
• Matching detectors pick up absorbed signal
• Computer reconstructs a “slice”
• Axial slices can be reconstructed in to a 3D pictures
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Human Neurobiology 217
Prof Stuart [email protected]
Magnetic Resonance Imaging 1
• An extremely powerful magnetic field is used to orientate the spin of atoms.
• A radio frequency pulse is used to cause some atoms to flip
• Energy given off tells a lot about the molecule the atom is in
• Can also be used to form images.
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Human Neurobiology 217
Prof Stuart [email protected]
CAT vs MRI• MRI (previously known as
nuclear magnetic resonance or NMR) is expensive.
• The magnet is supercooled with liquid helium in a liquid nitrogen blanket.
• Exposures are slow• No metal may enter the
field (no pacemakers etc.)
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Human Neurobiology 217
Prof Stuart [email protected]
Ultrasound• Ultrasound produced by a
piezoelectric crystal or array• No harm? Local heating and
cavitation?• Doppler effect raises frequency
as blood flows towards detector, lowers frequency in the opposite direction
• Can map blood flow speed• Can detect vasospasm (a
potentially lethal sequalae to a stroke)
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Human Neurobiology 217
Prof Stuart [email protected]
Positron Emission Tomography• Inject a very short lived
(radioactive) isotope with extra proton into the internal carotid.
• Produced in an (adjacent) cyclotron
• Gives out a positron, leaving a neutron.
• Positron anhilated when it hits and electron.
• Produces two photons in opposite directions
• Simultaneity detectors record the event.
Choice of labelled compound determines the result (transmitter etc.)
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Human Neurobiology 217
Prof Stuart [email protected]
fMRI
• By targeting protons in hydroxyl groups can measure blood flow
• Areas of high flow = areas of high activity.
• Usual advantages of MRI (see previous slide)
• No radioactivity needed, replacing PET
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Human Neurobiology 217
Prof Stuart [email protected]
Deep Infrared
• New technique• Involves use of far
infrared to penetrate the skull
• Reflected light picked up• Reflected better by areas
of high blood flow• Experimental, low
resolution as yet.
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Human Neurobiology 217
Prof Stuart [email protected]
SQUIDS• Supercooled, quantum
interference devices• Can pick up minute
magnetic fields created by the activity of cells.
• More localised than EEGs, not an “average”
• Low resolution as the detectors are large
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Human Neurobiology 217
Prof Stuart [email protected]
EEGs • Extra cerebral recordings average all the electrical
activity going on in the brain• Widespread changes can be picked up (epilepsy, coma,
REM sleep etc.)